Germanium compound delivery device

ABSTRACT

Germanium compounds suitable for use as vapor phase deposition precursors for germanium films are provided. Methods of depositing films containing germanium using such compounds are also provided. Such germanium films are particularly useful in the manufacture of electronic devices.

This application is a divisional of application Ser. No. 10/816,356,filed on Apr. 2, 2004, now allowed, which claims the benefit ofprovisional application Ser. No. 60/460,791, filed on Apr. 5, 2003, andprovisional application Ser. No. 60/513,475, filed on Oct. 22, 2003, andprovisional application No. 60/513,476, filed on Oct. 22, 2003.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of germaniumcompounds. In particular, the present invention relates to the certaingermanium compounds suitable for use in vapor deposition processes.

Metal films may be deposited on surfaces, such as non-conductivesurfaces, by a variety of means such as chemical vapor deposition(“CVD”), physical vapor deposition (“PVD”), and other epitaxialtechniques such as liquid phase epitaxy (“LPE”), molecular beam epitaxy(“MBE”), chemical beam epitaxy (“CBE”) and atomic layer deposition(“ALD”). Chemical vapor deposition processes, such as metalorganicchemical vapor deposition (“MOCVD”), deposit a metal layer bydecomposing organometallic precursor compounds at elevated temperatures,i.e., above room temperature, either atmospheric pressure or at reducedpressures. A wide variety of metals may be deposited using such CVD orMOCVD processes.

For semiconductor and electronic device applications, theseorganometallic precursor compounds must be highly pure and besubstantially free of detectable levels of both metallic impurities,such as silicon and zinc, as well as oxygenated impurities. Oxygenatedimpurities are typically present from the solvents used to prepare suchorganometallic compounds, and are also present from other adventitioussources of moisture or oxygen.

For certain applications where high speed and frequency response of anelectronic device is desired, silicon-only devices, e.g. silicon bipolartransistors, perform marginally and the introduction of germanium isnecessary to obtain the desired functionality. In a heterojunctionbipolar transistor (“HBT”), a thin silicon-germanium layer is grown asthe base of a bipolar transistor on a silicon wafer. Thesilicon-germanium HBT has significant advantages in speed, frequencyresponse, and gain when compared to a conventional silicon bipolartransistor. The speed and frequency response of a silicon-germanium HBTare comparable to more expensive gallium-arsenide HBTs.

The higher gain, speeds, and frequency response of silicon-germaniumHBTs have been achieved as a result of certain advantages ofsilicon-germanium not available with pure silicon, for example, narrowerband gap and reduced resistivity. Silicon-germanium may be epitaxiallygrown on a silicon substrate using conventional silicon processing andtools. This technique allows one to engineer device properties such asthe energy band structure and carrier mobility. For example, it is knownin the art that grading the concentration of germanium in thesilicon-germanium base builds into the HBT device an electric field orpotential gradient, which accelerates the carriers across the base,thereby increasing the speed of the HBT device compared to asilicon-only device. A common method for fabricating silicon andsilicon-germanium devices is by CVD. A reduced pressure chemical vapordeposition technique (“RPCVD”) used to fabricate the HBT device allowsfor a controlled grading of germanium concentration across the baselayer as well as precise control over the doping profile.

Germane (GeH₄) is the conventional precursor for germanium deposition.Germane is a gas under standard conditions and is difficult to handle.As germane is toxic, processes employing germane require extensivesafety procedures and equipment. Germane typically requires film growthtemperatures of approximately 500° C. for thermal CVD applications. Suchdecomposition temperatures are not always suitable, such as inapplications where there is a need for lower temperatures, e.g. 200° C.Other CVD applications require higher growth temperatures, e.g.700-1100° C., which cause germane to break up prematurely which, inturn, leads to the formation of particles and a reduction in metal filmgrowth rates. A further problem with germanium precursors arises insilicon-germanium deposition when a relatively stable silicon precursorand a relatively unstable germanium precursor (germane) are used todeposit a silicon-germanium film, the differences in precursor stabilitymakes control of the silicon-germanium composition difficult.

U.S. Patent Application No. 2003/0111013 (Oosterlaken et al.) disclosesan apparatus for the deposition of silicon germanium layers. Thisapplication discloses certain source compounds for the vapor depositionof germanium, such as mono-, di- tri- and tetra-chlorogermanes. Suchcompounds may not be suitable for all germanium vapor depositionapplications as their decomposition temperatures may be too low. Forexample, monochlorogermane is known to decompose at temperatures as lowas 25° C.

There remains a need for germanium precursors that offer an optimizeddeposition of germanium-containing films at various growth temperatures.Such growth temperatures determine the properties of thegermanium-containing film. A limitation in growth temperature limits thefull exploitation of the capabilities of a germanium-containing film.There remains a need for germanium precursors for CVD that are safer tohandle.

SUMMARY OF THE INVENTION

The present inventors have surprisingly found that the above limitationson the deposition of germanium by CVD can be remedied. The presentinvention provides a method of depositing a film containing germanium ona substrate including the steps of: a) conveying two or more germaniumcompounds in a gaseous phase to a deposition chamber containing thesubstrate, wherein a first germanium compound is a halogermaniumcompound of the formula X¹ _(4-a)GeR_(a), wherein a=0-3, each X¹ isindependently a halogen, and each R is independently chosen from H,alkyl, alkenyl, alkynyl, aryl, and NR⁴R⁶, wherein each R⁴ and R⁶ areindependently chosen from H, alkyl, alkenyl, alkynyl and aryl, andwherein a second germanium compound has the formula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b′≦3 when X¹=Cl, R=H, and X=Cl; b)decomposing the two or more germanium compounds in the depositionchamber; and c) depositing the film comprising germanium on thesubstrate.

Further, the present invention provides a method of manufacturing anelectronic device including the step of depositing a film containinggermanium on a substrate wherein the film including the steps of: a)conveying two or more germanium compounds in a gaseous phase to adeposition chamber containing the substrate, wherein a first germaniumcompound is a halogermanium compound of the formula X¹ _(4-a)GeR_(a),wherein a=0-3, each X¹ is independently a halogen, and each R isindependently chosen from H, alkyl, alkenyl, alkynyl, aryl, and NR⁴R⁶,wherein each R⁴ and R⁶ are independently chosen from H, alkyl, alkenyl,alkynyl and aryl, and wherein a second germanium compound has theformula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b′≦3 when X¹ =Cl, R=H, and X=Cl; b)decomposing the two or more germanium compounds in the depositionchamber; and c) depositing the film comprising germanium on thesubstrate.

The present invention also provides a composition including two or moregermanium compounds; wherein a first germanium compound is ahalogermanium compound of the formula X¹ _(4-a)GeR_(a), wherein a=0-3,each X¹ is independently a halogen, and each R is independently chosenfrom H, alkyl, alkenyl, alkynyl, aryl, and NR⁴R⁶, wherein each R⁴ and R⁶are independently chosen from H, alkyl, alkenyl, alkynyl and aryl, andwherein a second germanium compound has the formula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b′≦3 when X¹ =Cl, R=H, and X=Cl.

Still further, the present invention provides a vapor delivery devicesuitable for feeding a fluid stream saturated with a germanium compoundsuitable for depositing a film containing germanium to a chemical vapordeposition system including a vessel having an elongated cylindricalshaped portion having an inner surface having a cross-section, a topclosure portion and a bottom closure portion, the top closure portionhaving an inlet opening for the introduction of a carrier gas and anoutlet opening, the elongated cylindrical shaped portion having achamber containing two or more germanium compounds; the inlet openingbeing in fluid communication with the chamber and the chamber being influid communication with the outlet opening. In one embodiment, the twoor more germanium compounds include a first halogermanium compound ofthe formula X¹ _(4-a)GeR_(a), wherein a=0-3, each X¹ is independently ahalogen, and each R is independently chosen from H, alkyl, alkenyl,alkynyl, aryl, and NR⁴R⁶, wherein each R⁴ and R⁶ are independentlychosen from H, alkyl, alkenyl, alkynyl and aryl, and a second germaniumcompound of the formula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b∝≦3 when X¹=Cl, R=H, and X=Cl.

Another embodiment of the present invention is an apparatus for vapordeposition of metal films including one or more devices for feeding afluid stream including two or more germanium compounds, such as thosedescribed above.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification, the following abbreviations shallhave the following meanings, unless the context clearly indicatesotherwise:° C.=degrees centigrade; mol =moles; g=gram;ca.=approximately; and μm=micron=micrometer. “Halogen” refers tofluorine, chlorine, bromine and iodine and “halo” refers to fluoro,chloro, bromo and iodo. Likewise, “halogenated” refers to fluorinated,chlorinated, brominated and iodinated. “Alkyl” includes linear, branchedand cyclic alkyl. Likewise, “alkenyl” and “alkynyl” include linear,branched and cyclic alkenyl and alkynyl, respectively. The term “SiGe”refers to silicon-germanium. As used herein, “CVD” is intended toinclude all forms of chemical vapor deposition such as MOCVD, MOVPE,OMVPE, OMCVD and RPCVD. The articles “a” and “an” refer to the singularand the plural.

Unless otherwise noted, all amounts are percent by weight and all ratiosare molar ratios. All numerical ranges are inclusive and combinable inany order except where it is clear that such numerical ranges areconstrained to add up to 100%.

The present invention provides a method of depositing a film containinggermanium on a substrate including the steps of: a) conveying two ormore germanium compounds in a gaseous phase to a deposition chambercontaining the substrate, wherein a first germanium compound is ahalogermanium compound of the formula X¹ _(4-a)GeR_(a), wherein a=0-3,each X¹ is independently a halogen, and each R is independently chosenfrom H, alkyl, alkenyl, alkynyl, aryl, and NR⁴R⁶, wherein each R⁴ and R⁶are independently chosen from H, alkyl, alkenyl, alkynyl and aryl, andwherein a second germanium compound has the formula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b′≦3 when X¹=Cl, R=H, and X=Cl; b)decomposing the two or more germanium compounds in the depositionchamber; and c) depositing the film comprising germanium on thesubstrate. In one embodiment, the second germanium compound is an alkylgermane. Exemplary alkyl germanes include, without limitation, thosecompounds having the above formula where a′=c′=0, d′=2-3, and b′=1-2. Ina further embodiment, the alkyl germanium compound is a heterolepticalkyl germanium compound. By “heteroleptic alkyl germanium compound” ismeant a germanium compound having mixed alkyl groups, i.e., a germaniumcompound having two or more alkyl groups where at least two of the alkylgroups are different. Exemplary heteroleptic alkyl germanium compoundsinclude those of the formula R⁵ _(z)GeH_(y); wherein each R⁵ isindependently chosen from alkyl, alkenyl, alkynyl and aryl; z=2-3; andy=1-2.

In another embodiment, at least two halogermanium compounds are used. Asused herein, the term “halogermanium compound” refers to any germaniumcompound having one or more halogens bonded directly to the germanium.The present halogermanium compounds may have a wide variety of othergroups bonded to the germanium, provided that at least one halogen isbonded to the germanium. It will be clear to those skilled in the artthat three, four or more different germanium compounds, particularlyhalogermanium compounds, may be advantageously used in the presentinvention.

A wide variety of halogermanium compounds may be used, such as, but notlimited to, tetrahalogermanes and halogermanium compounds of the formulaX¹ _(4-a)GeR_(a), wherein each R is independently chosen from H, alkyl,alkenyl, alkynyl, aryl and NR¹R²; R¹ and R² are independently chosenfrom H, alkyl, alkenyl, alkynyl and aryl; each X¹ is independentlyhalogen; and a=0-3. The tetrahalogermanes have the formula GeX¹ ₄,wherein each X is independently a halogen. When two or more halogens arepresent in the halogermanium compounds, such halogens may be the same ordifferent.

A wide variety of alkyl, alkenyl and alkynyl groups may be used for R,R¹ and R². Suitable alkyl groups include, without limitation,(C₁-C₁₂)alkyl, typically (C₁-C₆)alkyl and more typically (C₁-C₄)alkyl.Exemplary alkyl groups include, but are not limited to, methyl, ethyl,n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl,cyclopentyl, hexyl, and cyclohexyl. More typically, suitable alkylgroups include ethyl, iso-propyl, and tert-butyl. Suitable alkenylgroups include, without limitation, (C₂-C₁₂)alkenyl, typically(C₂-C₆)alkenyl and more typically (C₂-C₄)alkenyl. Exemplary alkenylgroups include vinyl, allyl, methallyl and crotyl. Typical alkynylgroups include, without limitation, (C₂-C₁₂)alkynyl, typically (C₂-C₆)alkynyl and more typically (C₂-C₄)alkynyl. Suitable aryl groups are(C₆-C₁₀)aryl, including, but not limited to, phenyl, tolyl, xylyl,benzyl and phenethyl. When two or more alkyl, alkenyl or alkynyl groupsare present, such groups may be the same or different.

Typical amino (NR¹R²) groups for R include, but are not limited to,dimethylamino, diethylamino, di-iso-propylamino, ethylmethylamino,iso-propylamino, and tert-butylamino. However, other suitable aminogroups may be used. Any of the above alkyl, alkenyl, alkynyl or arylgroups of R, R¹ and R² may optionally be substituted with one or moreamino (NR⁴R⁶) groups, wherein R⁴ and R⁶ are independently chosen from H,alkyl, alkenyl, alkynyl and aryl. By “substituted” it is meant that oneor more hydrogens on the alkyl, alkenyl, alkynyl or aryl group isreplaced with one or more NR⁴R6 groups. Exemplary alkyl substituted withNR⁴R⁶ groups include, without limitation, dimethylamino-methyl((CH₃)₂N—CH₂-), dimethylamino-ethyl ((CH₃)₂N—C₂H₄-), diethylamino-ethyl((C₂H₅)₂N—C₂H₄-), dimethylamino-propyl ((CH₃)₂N—C₃H₆-), anddiethylamino-propyl ((C₂H₅)₂N—C₃H₆-).

Exemplary halogermanium compounds include, without limitation: thetetrahalogermanium compounds such as tetrachloro germane, tetrafluorogermane, tetrabromo germane, tetraiodo germane, chloro tribromo germane,dichloro dibromo germane, trichloro bromo germane, trichloro iodogermane, dichloro diiodo germane, trichloro iodo germane, tribromo iodogermane, dibromo diiodo germane, bromo triiodo germane, dichloro bromoiodo germane, chloro dibromo iodo germane, chloro bromo diiodo germane,trichloro fluoro germane, dichloro difluoro germane, chloro trifluorogermane, tribromo fluoro germane, dibromo difluoro germane, bromotrifluoro germane, iodo trifluoro germane, diiodo difluoro germane,triiodo fluoro germane, chloro bromo iodo fluoro germane, dichloro bromofluoro germane, chloro dibromo fluoro germane, dibromo iodo fluorogermane, bromo diiodo fluoro germane, dichloro iodo fluoro germane andchloro diiodo fluoro germane; and iso-propyl (dimethylamino) germaniumdichloride; methyl (dimethylamino) germanium dichloride; methyl(dimethylamino) germanium dibromide; dichloro (diethylamino) germane;dichloro ethyl (diethylamino) germane; dichloro tert-butyl(diethylamino) germane; dichloro bis(dimethylamino) germane; and chloroethyl (dimethylaminopropyl) (dimethylamino) germane; dichloro tert-butyl(dimethylamino) germane; chloro di-iso-propyl (dimethylamino) germane;trimethyl germanium chloride; methyl germanium trichloride; trimethylgermanium fluoride; trimethyl germanium bromide; tris(trifluoromethyl)germanium iodide; methyl germanium trifluoride; dimethyl germaniumdifluoride; dichloro methyl germane; dimethyl germanium dichloride;trimethyl germanium iodide; vinyl germanium trichloride; ethyl germaniumtrichloride; chloro tert-butyl dimethyl germane; allyl germaniumtrichloride; iso-butyl germanium trichloride; tert-butyl germaniumtrichloride; diethyl germanium dichloride; trimethyl germanium chloride;n-butyl germanium trichloride; trimethyl germanium bromide; di-n-butylgermanium dichloride; phenyl germanium dichloride; tri-n-butyl germaniumbromide; tri-n-butyl germanium chloride; and benzyl germaniumtrichloride.

Exemplary germanium compounds, suitable for use as the second germaniumcompound, include without limitation: germane, alkyl germanes such astetramethyl germane, tetraethyl germane, tetra-n-propyl germane, methylgermane, dimethyl germane, trimethyl germane, ethyl germane, diethylgermane, trimethyl germane, dimethyl diethyl germane, tert-butyl methylgermane, tert-butyl dimethyl germane, tert-butyl triethyl germane,tert-butyl ethyl germane, tert-butyl diethyl germane, tert-butyltrimethyl germane, tert-butyl iso-propyl germane, methyl tert-butyliso-propyl germane, iso-propyl germane, di-iso-propyl germane,di-iso-propyl dimethyl germane, tri-iso-propyl germane, tri-iso-propylmethyl germane, tert-butyl germane, iso-butyl germane, n-propyl germaneand di-iso-propyl diethyl germane; amino germanes such as(dimethylamino) germane, bis-(dimethylamino) germane, methyl(dimethylamino) germane, ethyl (dimethylamino) germane, diethyl(diethylamino) germane, tert-butyl (dimethylamino)germane, tert-butylbis(dimethylamino) germane, ethyl tert-butyl bis(dimethylamino) germane,iso-propyl (dimethylamino)germane, iso-propyl (diethylamino) germane,di-iso-propyl bis(dimethylamino) germane, n-propyl (dimethylamino)germane, and n-propyl (diethylamino) germane; and halogermaniumcompounds such as tert-butyl dimethyl germanium chloride, tert-butyldimethyl germanium bromide, tert-butyl diethyl germanium chloride,tert-butyl diethyl germanium iodide, dimethyl germanium dichloride,trimethyl germanium chloride, trimethyl germanium bromide, tert-butylgermanium trichloride, iso-butyl germanium trichloride, iso-propylgermanium chloride, iso-propyl germanium trichloride, di-iso-propylgermanium dibromide, iso-propyl dimethyl germanium chloride, iso-propylmethyl germanium dichloride, and iso-propyl dimethyl germanium bromide.

The two or more germanium compounds may be present in a wide range ofratios, such as in a mole ratio of 1:99 to 99:1. Typically, the twogermanium compounds, such as two halogermanium compounds, are present ina mole ratio of 25:75 to 75:25, and more typically from 35:65 to 65:35.In one embodiment, at least two halogermanium compounds are present. Inanother embodiment, at least one halogermanium compound, particularly atetrahalogermanium compound, and germane are used.

In general, the two or more germanium compounds used in the presentinvention are selected such that the mixture of the germanium compoundsprovides a stable concentration of germanium source in the vapor phase.This is achieved by using a combination of two or more germaniumcompounds, wherein a first germanium compound is a halogermaniumcompound. Any germanium compound may be used as the second germaniumcompound, however a halogermanium compound is preferred. In oneembodiment, the two or more germanium compounds become very difficult toseparate once mixed. The more difficult it is to separate the mixedgermanium compounds, the more stable the concentration of the germaniumsource in the vapor phase. An advantage of the present invention is thatthe properties of a germanium source can be tailored to desired reactionconditions. For example, a germanium source having a certain vaporpressure can be prepared by combining two or more germanium compoundsthat individually do not have the desired vapor pressure. In thisillustration, a germanium compound having a vapor pressure higher thanthe desired vapor pressure and a germanium compound having a vaporpressure lower than that desired can be mixed to provide a germaniumsource having the desired vapor pressure. As used herein, “germaniumsource” refers to a vapor phase germanium compound or compounds that areprovided to a reactor for deposition of a film containing germanium.

A further advantage of the present invention is that the presence ofhalogens in the germanium compounds leads to the formation of hydrogenhalide acids in the vapor phase, such as gaseous hydrogen chloride andhydrogen fluoride. Such gaseous hydrogen halide acids are effective incleaning the reactor during use. For example, the gaseous hydrogenhalide acids may remove solid particles deposited along the reactorwalls, thus minimizing reactor maintenance.

The present halogermanium compounds may be prepared by a variety ofprocedures. Typically, such compounds are prepared starting from acompound of the formula GeY₄ where Y is a reactive group such as ahalogen, an acetate or a (C₁-C₄)alkoxy, with halogens being mosttypical. As used herein, a reactive group is any group attached to thegermanium that is displaced or exchanged in a subsequent reaction.

Dialkylamino-substituted halogermanium compounds may be prepared by thereaction of a dialkylamine in liquid or gaseous forms with a germaniumcompound having one or more reactive groups and more typically isprepared by the reaction of a dialkylamino lithium reagent with suchgermanium compound having one or more reactive groups. Such reactionsare typically performed in a hydrocarbon solvent, such as but notlimited to hexane, heptane, octane, nonane, decane, dodecane, toluene,and xylene. Preferably, such solvents are deoxygenated prior to use. Thesolvents may be deoxygenated by a variety of means, such as purging withan inert gas, degassing the solvent in vacuo, or a combination thereof.Suitable inert gases include argon, nitrogen and helium, and preferablyargon or nitrogen. For example, germanium tetrachloride may be reactedwith a sufficient amount of dialkylamino lithium reagent to provide adesired dialkylamino germanium halide compound. This reaction isillustrated in Equation 1.2LiNMe₂+GeCl₄→(NMe₂)₂GeCl₂+2LiCl  (1)

Alkyl, alkenyl, alkynyl and aryl substituted halogermanium compounds maybe prepared using Grignard or organolithium reactions. Such reactionsare well known to those skilled in the art. In a typical Grignardreaction, a compound having one or more reactive groups is reacted witha Grignard reagent, such as methyl magnesium bromide or allyl magnesiumbromide in an ethereal solvent. Typical ethereal solvents include,without limitation, diethyl ether, di-isopropyl ether, n-butyl ether,iso-pentyl ether, dihexyl ether, diheptyl ether, tetrahydrofuran,dioxane, monoglyme, diglyme, diethylene glycol dibutyl ether, diethyleneglycol monobutyl ether, ethylene glycol dibutyl ether, ethylene glycolmonohexyl ether, ethylene glycol monobenzyl ether, tetraethylene glycoldimethyl ether, triethylene glycol dimethyl ether, butyl phenyl ether,and dicyclohexyl ether. Such solvents are typically deoxygenated priorto use as described above. This reaction is illustrated in Equation 2.(NMe₂)₂GeCl₂+AllylMgBr→(NMe₂)₂Ge(Allyl)Cl+MgBrCl  (2)

In a typical organolithium reaction, a compound having one or morereactive groups is reacted with an organolithium reagent, such as methyllithium, tert-butyl lithium, n-butyl lithium and phenyl lithium in ahydrocarbon solvent. Suitable solvents are those described above for thedialkylamino lithium reaction. Equation 3 illustrates the reaction ofbis(dimethylamino) germanium dichloride with iso-propyl lithium.(NMe₂)₂GeCl₂+i-PrLi→(NMe₂)₂Ge(i-Pr)Cl+LiCl  (3)

In another embodiment, a germanium compound having two or more reactivegroups may be reacted with two different lithium reagents in one pot.Such different lithium reagents may be two different organolithiumreagents, two different dialkylamino lithium reagents or a mixture of anorganolithium reagent and a dialkylamino lithium reagent. In suchreaction, the different lithium reagents may be added to the reactionsimultaneously or in a stepwise manner. Equation 4 illustrates thisreaction sequence for the reaction of germanium tetrachloride withtert-butyl lithium and dimethylamino lithium.t-BuLi+GeCl₄+LiNMe₂→(NMe₂)(tBu)GeCl₂+2LiCl  (4)

In a further embodiment, the alkyl-, alkenyl-, alkynyl- andaryl-substituted germanes may be prepared by a transalkylation reactionusing the appropriately substituted aluminum compound. For example,methyl-substituted germanes may be prepared by the reaction of anappropriate amount of trimethylaluminum with an appropriate amount ofgermanium tetrachloride in the presence of a tertiary amine. Suchamounts are well within the ability of those skilled in the art.Equation 5 illustrates this reaction sequence for the reaction ofgermanium tetrachloride with trimethylaluminum.2GeCl₄+AlMe₃→2MeGeCl₃+MeAlCl₂  (5)

Such transalkylation reactions using alkyl aluminum compounds arepreferably performed in the presence of a tertiary amine. Any tertiaryamine may suitably be used. Exemplary tertiary amines include, but arenot limited to, those having the general formula NR′R″R′″, wherein R″,R″ and R′″ are independently selected from (C₁-C₆)alkyl,di(C₁-C₆)alkylamino-substituted (C₁-C₆)alkyl, and phenyl and wherein R′and R″ may be taken together along with the nitrogen to which they areattached to form a 5-7 membered heterocyclic ring. Such heterocyclicring may be aromatic or non-aromatic. Particularly suitable tertiaryamines include, but are not limited to, trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-iso-propylamine,tri-iso-butylamine, dimethylaminocyclohexane, diethylaminocyclohexane,dimethylaminocyclopentane, diethylaminocyclopentane,N-methylpyrrolidine, N-ethylpyrrolidine, N-n-propylpyrrolidine,N-iso-propylpyrrolidine, N-methylpiperidine, N-ethylpiperidine,N-n-propylpiperidine, N-iso-propylpiperidine, N,N′-dimethylpiperazine,N,N′-diethylpiperazine, N,N′-dipropylpiperazine,N,N,N′,N′-tetramethyl-1,2-diaminoethane, pyridine, pyrazine, pyrimidine,and mixtures thereof. Preferred amines include trimethylamine,triethylamine, tri-n-propylamine, tri-iso-propylamine, andtri-n-butylamine. More preferably, the tertiary amine is triethylamineor tri-n-propylamine. It will be appreciated by those skilled in the artthat more than one tertiary amine may be used in the present invention.Such tertiary amines are generally commercially available from a varietyof sources. Such tertiary amines may be used as is or, preferablyfurther purified prior to use.

Halogermanes containing one or more germanium-hydrogen bonds can beprepared by a variety of methods known in the literature. For example,elemental germanium can be reacted with a gaseous mineral acid, such asgaseous hydrogen chloride, to produce halogermanes. See Equation 6.Ge⁰+2HCl(g)→H₂GeCl₂  (6)Alternatively, germane (GeH₄) may be reacted with a tetrahalogermane,typically in the presence of a catalyst such as AlCl₃, to producehalogermanes. The particular halogermane obtained will depend upon thestoichiometry of the starting materials.

In each of the above described reactions, the mole ratio of reagent tothe germanium compound depends upon the number of reactive groups in thegermanium compound that are to be exchanged. Typically, the mole ratioof any of the above reagents to the reactive group is from 1:1 to 1.3:1.Accordingly, if two reactive groups in the germanium compound are to beexchanged, the mole ratio of reagent to germanium compound is from 2:1to 2.6:1, which corresponds to a mole ratio of reagent to reactive groupof 1:1 to 1.3:1. Other amounts and ratios may be used depending upon thespecific reaction conditions employed.

It will be appreciated by those skilled in the art that the order of theabove reactions may be performed in any order. Typically, any step ofreducing a germanium-halide compound to form a germanium-hydrogencompound will be performed last, although other orders of reaction maybe advantageous.

Any of the above described methods of preparing the desiredhalogermanium precursor compounds may be performed in a batch,semi-batch, continuous or semi-continuous mode. For example, the presentinvention provides a batch as well as semi-continuous process for thepreparation of halogermanium compounds, including the steps ofdelivering a germanium compound and alkylating agent independently to areaction zone maintained at a predetermined temperature sufficient toallow the alkylation to proceed and the product is then separated oncethe reaction is complete. The halogermanium product is collected at theoutlet preferably located at the top of the reactor while the byproductin non-vaporized state is removed as waste from the reactor at the endof the reaction. The addition of reagents in a multi-step alkylation maybe either in a simultaneous or sequential manner. The rate of additionof the various reagents may be controlled by using appropriate flowcontrollers that are known in the art.

An advantage of the present invention is that the two or more germaniumcompounds are substantially free of metallic impurities such as zinc andaluminum, and preferably free of zinc and aluminum. In particular, suchgermanium compounds are substantially free of zinc, aluminum andsilicon, and preferably free of such impurities. By “substantially free”it is meant that the compounds contain less than 0.5 ppm of suchimpurities, and preferably less than 0.25 ppm. In another embodiment,the present germanium compounds have “5-nines” purity, i.e. a purity of≧99.999%. More typically, the germanium compounds have a purity of“6-nines”, i.e. ≧99.9999%.

The present two or more germanium compounds, particularly two or morehalogermanium compounds, are suitable for use as precursors for thevapor phase deposition of germanium-containing epitaxial films, such asby LPE, ME, CBE, ALD and are particularly suitable for use as precursorsin CVD. More particularly, the germanium compounds are suitable for useas precursors in the vapor phase deposition of silicon-germanium(“SiGe”) films. Such films are useful in the manufacture of electronicdevices, such as integrated circuits, and optoelectronic devices, andparticularly in the manufacture of heterojunction bipolar transistors.

Suitable germanium compounds may be solids, liquids or gasses. When thegermanium compounds are solids, liquids or gases, they may be combinedinto a single delivery device, such as a bubbler. For example, two ormore gases, two or more liquids, two or more solids, or a combination ofliquid and solid germanium compounds may be combined into a singledelivery device. Alternatively, multiple delivery devices may be used.For example, a first germanium compound may be added to a first deliverydevice and a second germanium compound may be added to a second deliverydevice. It will be appreciated by those skilled in the art that eitherthe first delivery device, the second delivery device or both deliverydevices contain more than one germanium compound. It will be furtherappreciated that more than two delivery devices may be used. When one ormore gaseous germanium compounds, such as germane, are to be used withone or more solid or liquid germanium compounds, such as germaniumtetrachloride, it is preferred that the gaseous germanium compounds arenot in the same delivery device as the solid and liquid germaniumcompounds.

In one embodiment, films including germanium are typically deposited byfirst placing the desired two or more halogermanium precursor compounds,i.e. source compounds, in a vapor delivery device having an outletconnected to a deposition chamber. A wide variety of vapor deliverydevices may be used, depending upon the particular deposition apparatusused. When the precursor compound mixture is a solid, the devicesdisclosed in U.S. Pat. Nos. 6,444,038 (Rangarajan et al.) and 6,607,785(Timmons et al.), as well as other designs, may be used. For liquidprecursor compound mixtures, the devices disclosed in U.S. Pat. Nos.4,506,815 (Melas et al) and 5,755,885 (Mikoshiba et al) may be used, aswell as other liquid precursor vapor delivery devices. The sourcecompound mixture is maintained in the vapor delivery device as a liquidor solid. Solid source compounds are typically vaporized or sublimedprior to transportation to the deposition chamber.

In another embodiment, a first halogermanium compound may be placed in afirst vapor delivery device and a second germanium compound, such as asecond halogermanium compound, may be placed in a second vapor deliverydevice. Each vapor delivery device is then connected to the samedeposition apparatus. Each of the germanium compounds is then conveyedfrom its respective delivery device into the deposition chamber toprovide two germanium compounds in the vapor phase. It will beappreciated that more than two vapor delivery devices containinggermanium compounds may be used in order to provide more than twogermanium compounds in the vapor phase. In a further embodiment, the twoor more germanium compounds are placed in a single delivery device.

In a still further embodiment, a first germanium compound, such asgermane, is placed in a first vapor delivery device and a secondgermanium compound, particularly a halogermanium compound such asgermanium tetrachloride, germanium tetrabromide and combinationsthereof, are placed in a second vapor delivery device. Both thegermanium compound and the halogermanium compound are delivered to adeposition chamber in the vapor phase. Such germanium compound andhalogermanium compound, in one embodiment, may react in the vapor phaseto form a single compound germanium source. In this way, a stableconcentration of germanium source in the vapor phase is provided.

Accordingly, the present invention provides a vapor delivery device forfeeding a fluid stream saturated with a germanium compound suitable fordepositing a film containing germanium to a chemical vapor depositionsystem including a vessel having an elongated cylindrical shaped portionhaving an inner surface having a cross-section, a top closure portionand a bottom closure portion, the top closure portion having an inletopening for the introduction of a carrier gas and an outlet opening, theelongated cylindrical shaped portion having a chamber containing two ormore germanium compounds as described above; the inlet opening being influid communication with the chamber and the chamber being in fluidcommunication with the outlet opening.

In another embodiment, the present invention provides an apparatus forchemical vapor deposition of metal films including one or more of thevapor delivery devices for feeding a fluid stream saturated with two ormore germanium compounds described above. Such vapor delivery devicesmay be used to provide the germanium compounds in the vapor phase to asingle deposition chamber or to a plurality of deposition chambers.

The source compounds are typically transported to the deposition chamberby passing a carrier gas through the vapor delivery device. Suitablecarrier gasses include nitrogen, hydrogen, and mixtures thereof. Ingeneral, the carrier gas is introduced below the surface of the sourcecompounds, and bubbles up through the source compounds to the headspaceabove it, entraining or carrying vapor of the source compounds in thecarrier gas. The entrained or carried vapor then passes into thedeposition chamber.

The deposition chamber is typically a heated vessel within which isdisposed at least one, and possibly many, substrates. The depositionchamber has an outlet, which is typically connected to a vacuum pump inorder to draw by-products out of the chamber and to provide a reducedpressure where that is appropriate. MOCVD can be conducted atatmospheric or reduced pressure. The deposition chamber is maintained ata temperature sufficiently high to induce decomposition of the sourcecompound. The deposition chamber temperature is from 200° to 1200° C.,the exact temperature selected being optimized to provide efficientdeposition. Optionally, the temperature in the deposition chamber as awhole can be reduced if the substrate is maintained at an elevatedtemperature, or if other energy such as radio frequency (“RF”) energy isgenerated by an RF source.

Suitable substrates for deposition, in the case of electronic devicemanufacture, may be silicon, gallium arsenide, indium phosphide,sapphire, and the like. Such substrates are particularly useful in themanufacture of integrated circuits.

Deposition is continued for as long as desired to produce a filmincluding germanium having the desired properties. Typically, the filmthickness will be from several tens of nanometers to several hundreds ofmicrons.

The present invention further provides a method for manufacturing anelectronic device including the step of depositing a film includinggermanium on an electronic device substrate including the steps of: a)conveying two or more germanium compounds in a gaseous phase to adeposition chamber containing the substrate, wherein a first germaniumcompound is a halogermanium compound of the formula X¹ _(4-a)GeR_(a),wherein a=0-3, each X¹ is independently a halogen, and each R isindependently chosen from H, alkyl, alkenyl, alkynyl, aryl, and NR³R⁴,wherein each R³ and R⁴ are independently chosen from H, alkyl, alkenyl,alkynyl and aryl, and wherein a second germanium compound has theformula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b′≦3 when X¹=Cl, R=H, and X=Cl; b)decomposing the two or more germanium compounds in the depositionchamber; and c) depositing the film comprising germanium on thesubstrate.

The present invention is particularly suitable for the deposition ofgermanium-containing films, such as SiGe films. SiGe films are beingemployed for two technologies. One well-established major application isBipolar CMOS or BiCMOS where a thin (40 to 80 nm) SiGe film is used asthe base of a high frequency HBT. The substrate for the deposition ofthis SiGe base film and the subsequent Si collector film is a highlystructured silicon wafer with the CMOS circuitry mostly finished. Theother application for SiGe CVD is the area of strained silicon or s═Si.Here a deposition of a thick 3 to 5 micrometer SiGe layer takes place ona plain silicon wafer. Subsequent to the growth of the SiGe film a thin(20 nm) Si film is grown. This silicon film adopts the crystal latticeof the underlying SiGe layer (strained silicon). Strained silicon showsmuch faster electrical responses than regular silicon.

In another embodiment, a method for fabricating a device containing agroup of silicon-germanium layers is illustrated by the steps of: i)providing a substrate including a surface layer of a group IV element,ii) maintaining the substrate at a temperature ranging from 400° C. to600° C., iii) forming a layer of Si_(1-x)Ge_(x), where x ranges from 0to 0.50, on the substrate by MOCVD using two or more of theabove-described germanium compounds; iv) maintaining the substrate atabout the temperature of step i) and continuing a silicon precursor flowwith a flow of the germanium compounds completely switched off, in orderto obtain abrupt interfaces, and v) maintaining the substrate at aboutthe temperature of step i), and forming a cap layer of strained silicon,thereby improving the mobility of electrons and speed of the device.

The following examples are expected to illustrate further variousaspects of the present invention, but are not intended to limit thescope of the invention in any aspect. All manipulations are performed inan inert atmosphere, typically under an atmosphere of dry nitrogen.

EXAMPLE 1

Dimethylamino germanium trichloride is expected to be synthesizedaccording to the equation:LiNMe₂+GeCl₄→(NMe₂)GeCl₃+LiCl

To a stirred solution of germanium tetrachloride (50 g, 0.233 moles) inpentane (100 mL) maintained at 0° C., is added dropwise a solution oflithium dimethylamide in diethyl ether (11.898 g, 0.233 moles, 50 mL)via pressure equalized addition funnel. The addition lasts forapproximately 30 minutes. When the addition is completed, the resultingmixture is allowed to slowly warm to room temperature after which asuspension is expected to be obtained.

When the suspension settles, the supernatant mother liquor is separatedusing a siphon technique. The precipitate of lithium chloride byproductis washed with fresh pentane and the washings are separated via siphonunder nitrogen atmosphere, and are subsequently combined with the motherliquor. The pentane/ether solvents are then removed via atmosphericpressure distillation by heating the reaction mass to 60° C. Theexpected crude product obtained may be further purified by vacuumdistillation and is expected to yield high purity (dimethylamino)germanium trichloride free of metallic impurities and organic solvents.

EXAMPLE 2

To a conventional vapor delivery device are added (dimethylamino)germanium trichloride and germanium tetrachloride in an expected molarratio of 45:55.

EXAMPLE 3

The procedure of Example 2 is repeated except that the germaniumcompounds in the table are expected to be used in the molar ratiosshown. The molar ratios reported are the expected moles of halogermaniumcompound: second germanium compound. Second Germanium SampleHalogermanium Compound Compound Molar Ratio A GeCl₄ Me₄Ge 95:5  B GeCl₄t-Bu(Me)GeH₂ 70:30 C GeCl₄ i-PrGeMe₃ 25:75 D GeBr₄ Me₄Ge 80:20 E GeBr₄(H₂C═CH)GeMe₃ 40:60 F GeBr₄ t-BuGeH₃  5:95 G GeI₄ Et₂GeCl₂ 70:30 H GeI₄(NMe₂)GeCl₃ 45:55 I GeI₄ (NMe₂)GeCl₃ 20:80 J Me₃GeCl t-Bu(Me)GeH₂ 95:5 K Me₃GeCl t-Bu(Me)GeH₂ 22:78 L Me₃GeCl i-PrGe Me₃ 65:35 M MeGeCl₃ Et₄Ge90:10 N MeGeCl₃ (H₂C═CH)GeMe₃ 35:65 O MeGeCl₃ i-PrGeMe₃ 10:90 Pt-BuGeCl₃ (NMe₂)GeCl₃ 50:50 Q t-BuGeCl₃ Me(NMe₂)GeCl₂ 38:62 R t-BuGeCl₃t-BuGeH₃ 25:75 S H₂GeCl₂ Me₂(i-Pr)GeH 57:43 T GeCl₄ GeBr₄ 22:78 U GeBr₄HGeCl₃ 42:58 V Et₂GeBr₂ t-Bu(NMe₂)GeCl₂ 30:70 W Me₂GeHCl i-Pr(Me)GeH₂47:53 X MeGeHCl₂ Me(Et)GeH₂ 21:79 Y MeGeF₃ Me₂GeEt₂ 34:66 Z Me₂GeF₂Et₂(Me)GeH 15:85 AA i-BuGeCl₃ i-BuGeH₃ 50:50 BB n-PrGeCl₃ n-PrGeH₃ 42:58

In the above table, the following abbreviations are used: Me=methyl,Et=ethyl, i-Pr=iso-propyl n-Pr-n-propyl, i-Bu-iso-butyl andt-Bu=tert-butyl.

EXAMPLE 4

A germanium film is expected to be grown on a sapphire substrate usingthe delivery device of Example 3 containing Sample B attached to a MOCVDapparatus. The delivery device is heated and a carrier gas (H₂ and/orN₂) is passed through the heated delivery device. The carrier gassaturated with vapor phase germanium compounds is directed to adeposition chamber containing the sapphire substrate. The depositionchamber is maintained at a temperature sufficient to inducedecomposition of the vapor phase germanium compounds. A germanium filmis expected to be deposited on the sapphire substrate. Deposition isexpected to be continued until a desired thickness of the germanium filmis achieved.

EXAMPLE 5

The procedure of Example 4 is repeated except that two delivery devicesare expected to be used. The first delivery device is expected tocontain tetrachlorogermane and the second delivery device is expected tocontain germane (GeH₄).

EXAMPLE 6

The procedure of Example 4 is repeated except that two delivery devicesare expected to be used, a first delivery device expected to containgermanium tetrachloride and a second delivery device expected to containtert-butyl methyl germane.

EXAMPLE 7

A group of Si_(x)Ge_(1-x) epitaxial structures are expected to be grownby MOCVD on (0001) sapphire substrates. A first delivery devicecontaining disilane is attached to a MOCVD apparatus. A second deliverydevice from Example 2 is attached to the MOCVD apparatus. The deliverydevices are heated and a carrier gas (H₂ and/or N₂) is passed througheach heated delivery device. The carrier gas saturated with vapor phasedisilane and the carrier gas saturated with vapor phase germaniumcompounds are directed to a deposition chamber containing the sapphiresubstrate. The deposition chamber is maintained at a temperaturesufficient to induce decomposition of the vapor phase compounds (e.g.650° C. and 750° C.). For this group of layers, a 1 to 2 μm thickSi_(0.9)Ge_(0.1) layer is expected to be first grown on a siliconsubstrate. Subsequent layers of composition Si_(0.8)Ge_(0.2),Si_(0.7)Ge_(0.3), and Si_(0.6)Ge_(0.4) are expected to be grown byincreasing the mass flow rate of the germanium precursors. Afterdeposition of the Si_(1-x)Ge_(x) graded layers, the silicon precursorflow is continued with the germanium precursor flow completely switchedoff, in order to obtain abrupt interfaces. Silicon deposition isexpected to be carried out using the graded SiGe as the underlyinglayer, and epitaxial strained silicon layer is deposited as the caplayer.

1. A vapor delivery device comprising a vessel having an elongatedcylindrical shaped portion having an inner surface having across-section, a top closure portion and a bottom closure portion, thetop closure portion having an inlet opening for the introduction of acarrier gas and an outlet opening, the elongated cylindrical shapedportion having a chamber containing two or more germanium compounds; theinlet opening being in fluid communication with the chamber and thechamber being in fluid communication with the outlet opening; wherein afirst germanium compound is a halogermanium compound of the formula X¹_(4-a)GeR_(a), wherein a=0-3, each X¹ is independently a halogen, andeach R is independently chosen from H, alkyl, alkenyl, alkynyl, aryl,and NR⁴R⁶, wherein each R⁴ and R⁶ are independently chosen from H,alkyl, alkenyl, alkynyl and aryl, and wherein a second germaniumcompound has the formula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; provided that a′+b′≦3 when X¹=Cl, R=H, and X=Cl.
 2. Thedelivery device of claim 1 wherein c′=1-3.
 3. The delivery device ofclaim 1 wherein a′=c′=0, b′=1-2 and d′=2-3.
 4. An apparatus for vapordeposition of metal films comprising the vapor delivery device ofclaim
 1. 5. An apparatus comprising a first vapor delivery devicecomprising a first germanium compound and a second vapor delivery devicecomprising a second germanium compound, the first and second vapordelivery devices capable of providing the first and second germaniumcompounds in the vapor phase to a deposition chamber, wherein the firstgermanium compound is a halogermanium compound of the formula X¹_(4-a)GeR_(a), wherein a=0-3, each X¹ is independently a halogen, andeach R is independently chosen from H, alkyl, alkenyl, alkynyl, aryl,and NR⁴R⁶, wherein each R⁴ and R⁶ are independently chosen from H,alkyl, alkenyl, alkynyl and aryl, and wherein the second germaniumcompound has the formula

wherein each R¹ and R² are independently chosen from H, alkyl, alkenyl,alkynyl and aryl; each R³ is independently chosen from alkyl, alkenyl,alkynyl and aryl; X is halogen; a′=0-4; b′=0-4; c′=0-3; d′=0-4 anda′+b′+c′+d′=4; wherein at least one of a′, c′and d′ is not 0; providedthat a′+b′≦3 when X¹=Cl, R=H, and X=Cl.